Studies will continue on the development and use of artificial blood substitutes based on perfluorochemicals and synthetic oncotic agents. Bloodless animals obtained by the complete exchange perfusion with such substitutes will be obtained routinely and should have srvival rates that are excellent. Such animals will replace missing cells and plasma proteins and continue to grow and develop. The bloodless animals will breathe 50 to 70 percent oxygen atmospheres and should show no oxygen toxicity symptoms even after five days of exposure. Bloodless rats will survive in 10 percent carbon monoxide for 17 to 24 hours and continue to live thereafter when returned to a CO-free atmosphere. This extraordinary protection against an otherwise lethal gas is probably afforded by the perfluorochemicals' capacity to deliver more than adequate quantities of oxygen to tissues even though these chemicals are also good solvents for CO. Normal rats given the artificial blood substitute are protected against 4 percent CO. These studies will be continued. The results suggest these preparations may hold promise in the treatment of CO-poisoning in man. New perfluorochemicals will be investigated as they become available. The artificial blood substitutes will also be used in organ perfusion experiments. BIBLIOGRAPHIC REFERENCES: Geyer, R.P. "Bloodless" rats through the use of artificial blood substitutes. Federation Proc. 34:1499, 1975. Geyer, R.P. Potential uses of artificial blood substitutes. Federation Proc. 34:1525, 1975.